1. Field of the Invention
The invention relates to a structure of a key switch for use in an input device of an information processing system, and more particularly, to a key switch of a low-profile structure.
2. Description of the Related Art
A conventional key switch has a structure wherein an elastic member with a cup-like shape is disposed above a membrane contact sheet. The membrane contact sheet has a pair of contacts placed opposite to each other and movable so as to come into contact with each other, and the elastic member can be pressed down from above with a key top. A stem extending downward is formed at the center on the underside of the key top so that, when the key top is pressed down, the stem causes the elastic member to undergo deformation downward. The membrane contact sheet is pressed down by the elastic member, and this brings the contacts placed opposite to each other into contact with each other. The stem is guided by a housing so as to be movable up and down, and enabling the key top to perpendicularly move straight up and down.
For effecting satisfactory vertical movement, a guide length, along which the stem is guided by the housing, needs to be set at not less than a given length. Also, for allowing the key top to move up and down perpendicularly even when an edge of the key top is pressed, the guide length along which the stem is guided by the housing needs to be set at not less than the given length. When the guide length is set at not less than the given length, however, the position of the key top tends to become higher. This makes such a key switch unsuitable for use in a portable personal computer and a word processor, of which there is strong demand for a lower profile type.